This invention relates to silicone-based coating compositions for the treatment of latex materials, particularly condoms and similar articles, which possess the advantage and characteristic that spermicidal agents are soluble in such compositions.
Latex materials are used for various applications, including the field of hygiene, for example as protective gloves, covers, protection for bandages, but especially for condoms.
In view of the growing risk of AIDS diseases, condoms are attracting increasing attention as protectives and prophylactics.
On the evidence of scientific investigations, the use of a condom as a genital HIV prophylactic affords the best possible protection at the present time (cf. Knut O. K. Hoffmann: Wie sicher ist das Kondom ? (How Safe is the Condom ?), ZFA 7/1988).
The industrial manufacture of the condom for around 65 years is attributable to Julius Fromm and has now reached a high standard in regard to the material quality of these articles. Latex is almost exclusively used for the production of condoms, being distinguished above all by its enormous tear strength, elasticity and imperviousness.
In addition, latex-based condoms can readily be produced in extremely thin layers having a thickness of the order of 0.08 mm. On account of the relatively poor slip properties of latex, a lubricant is generally applied after the production of these articles to minimize problems in use.
Whereas, previously, solid materials, such as talcum, were used, oil-like products are today mostly used for improving slip properties.
Several different lubricants or preparations are described in the patent literature, with particular significant advantages being attributed mainly to the glycols and classical methyl silicone oils.
For example, Japanese patent application JP 52 138 397 describes the use of fine glass microspheres in combination with silicone oil, various glycols, glycerol or modified alcohols, while JP 70 006 119 describes a system of silicone oil and pteridophyta spores.
In addition, JP 59 141 942 mentions silicone oils or water-soluble polymers for improving slip properties.
Combinations of modified alcohols, alginates, propylene glycol, gelatine, sodium chloride and saccharides (JP 74 019 799) and polyethylene glycol in combination with silicone oils (JP 62 164 460) have been described with particular regard to the spermicidal treatment of the lubricants.
Of the large number of useable systems, methyl silicone oils (PDMS) of medium viscosity are now preferably used as wet coating compositions because, by virtue of their high compatibility with mucous membrane, their favorable slip properties and their compatibility with latex, they afford advantages over glycols or other hydrophilic systems. In addition, PDMS are materials which are not contaminated by bacteria and, if properly used, may be regarded as extremely low in germs.
On account of the growing risk of possible infection with the HIV virus through sexual intercourse, greater importance than before is now being attributed to coating compositions which inhibit in vivo the activity of reverse transcriptase in HIV replication. From studies conducted by Hicks (cf. "Inactivation of HIV-III/LAV-infected cultures of normal human lymphocytes by Nonoxinol-9 in vitro", Lancet II, 1422-1423, 1985), it is known that such activity is observed in the case of spermicidal substances, for example of the Nonoxinol-9 type, a nonionic, surface-active substance.
Now, it would be desirable if substances such as these were soluble in the silicone oils hitherto used, although this is unfortunately not the case on account of the difference in chemical structure between the two classes of compounds.
Nonoxinol-9 has the chemical name 26-(4-nonylphenoxy)-3,6,9,12,15,18,21,24-octaoxahexacosan-1-ol and, in the broadest sense, is thus a modified polyether which is compatible with or soluble in glycols, polyglycols or polyethers.
Accordingly, glycol, polyglycol or a glycol-like system is almost exclusively used as carrier for Nonoxinol-9 for the spermicidal treatment of condoms. These hydrophilic substances generally show relatively poor wettability of the condom surface and less well pronounced compatibility with latex. In addition, they make the condom more tacky by comparison with PDMS.
The problem addressed by the present invention is to use silicone systems having solubility properties for active substances based on nonoxinol, preferably Nonoxinol-9, for the treatment of condoms to enable storable coating compositions with spermicidal activity to be produced.
In addition, these coating compositions would be fairly similar to PDMS in their properties, such as slip, tackiness and compatibility with mucous membrane.